The present invention relates to automotive vehicle transmissions and more particularly to a shift control mechanism for a manual transmission involving a plurality of forward drive positions and a reverse drive position. The control mechanism is specifically involved with controlling movement of the shift lever between one of the forward drive positions and the reverse drive position wherein these two positions lie in a linear path through which the shift lever moves therebetween. Erroneous shifting, which might occur if the shift lever were to be moved directly through said linear path from said one forward drive position to the reverse position, is prevented.
As is well known, a shift mechanism for a manual transmission having five forward drive positions and a reverse drive position is usually arranged with a shifting pattern wherein the shift lever is moved along three linear paths, with two drive positions being located at the opposite ends of each linear path. Thus, shifting of the transmission between a first and a second speed ratio is effected by moving the shift lever between two positions lying at the ends of one of said linear paths, with the third and fourth speed ratios being obtained by moving the shift lever to positions lying at the ends of a second linear path. The fifth speed ratio position and the reverse drive position are usually located at the ends of a third linear path of the shift lever, and when it is intended to downshift the transmission from the fifth or highest forward speed ratio during high speed vehicle operation, the shift lever could inadvertently be moved into the reverse drive position, thereby causing serious transmission damage and dangerous vehicle operating conditions.
Various mechanisms have been proposed to prevent such misshifting, among them being one which requires that the shift lever be pressed downwardly or pulled upwardly when it is to be moved into the reverse drive position. Another proposal has been to require manipulation of a button or the like independently of but concurrently with manipulation of the shift lever. In either case, however, such manipulation will present difficulties and require some skill on the part of a vehicle operator and it thus becomes difficult for the operator to accomplish such manipulations with ease during operation of the vehicle with the operator sitting at a normal position in the driver's seat. Moreover, the structure of such a transmission mechanism will inevitably involve undesirable complexity.
Accordingly, the present invention is intended to provide an improved shift control mechanism for use with a multiple forward speed manual transmission in which a transmission lever is activated by manipulation of a shift lever to selectively operate one of a plurality of fork shafts of the transmission in order to effect a reverse speed ratio and one forward speed ratio each of which lie at opposite ends of a linear path forming a part of the shifting pattern of the shift lever.
The invention provides a mechanism of the above type which operates to control the shifting operation which occurs between the reverse drive position and the one forward speed ratio position and, in one aspect thereof, the control mechanism is structured to prevent downshifting directly along a linear path of movement of the shift lever from the one forward drive position to the reverse position.
Furthermore, the mechanism of the invention operates to control shifting in the manner previously described without requiring other concurrent manipulative efforts, such as depression of a button or axial movement of a shift lever.